Add method to AccountAccess interface to get all accounts ordered by ID

This will allow clients to iterate over the entire list of registered users, 
ordered by the account ID.

Change-Id: Ic63827c3c9e2c8d6cde3ff8e38a820f8ee9d9495

gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/server/AccountAccess.java

@@ -46,4 +46,7 @@ public interface AccountAccess extends Access<Account, Account.Id> {
 
   @Query("ORDER BY accountId LIMIT ?")
   ResultSet<Account> firstNById(int n) throws OrmException;
+
+  @Query("ORDER BY accountId")
+  ResultSet<Account> all() throws OrmException;
 }